This invention relates to ultrasound and more particularly relates to determining quantitative movement, such as flow velocity, by using ultrasound.
Currently, most quantitative flow measurement done in ultrasound occurs along the scan axis, i.e., in the direction normal to the transducer face. If a method were devised that measured flow parallel to the transducer face, then the two could be combined to resolve the two-dimensional velocity vector in the scan plane. This concept would differ compared to existing lateral flow (i.e., movement parallel to the transducer face) measurement methods.
One method described by Newhouse and Reid (`Invariance of Doppler bandwidth with flow axis displacement`, IEEE Ultrasonics Symposium Proceedings, 1990, p1533), measures the variance of the Doppler signals returned from lateral flow. A technique developed by M Anderson (`Multi-dimensional velocity estimation with ultrasound using spatial quadrature`, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 45, no. 3, pp. 852-861) implements modified transducer apertures, creating ultrasound beams which produce modulated signals when scatters move laterally across the beam. Both these methods use no information from multiple ultrasound beam positions or scanning, and therefore differ from the techniques described in this specification. Another lateral flow method which measures direction and magnitude of local blood speckle pattern displacement using consecutive B-mode (i.e., gray scale) images was described by Trahey, Allison and Von Ramm (IEEE Transactions on Biomedical Engineering, vol. BME-34, No. 12, pp. 965-967). This technique requires multiple images and measures speckle position changes, unlike the preferred embodiment described in this specification which needs no such temporal measurements and estimates speckle size.